Process of deinking paper



Patented Feb. 5, 1935 UNITED STATES PATENT; OFFICE 1,990,376 a v raocnss or nnnvmc. mrnn No Drawing. Application August 6, 1934, SerialNo. 738,677

It is the object of my invention to remove ink from printed paper, and to obtain a resultant pulp suitable for working up into new paper with or without the incorporation of fresh paper stock.

Broadly speaking, I treat the paper to be deinked, desirably with beating and at elevated temperature, with a solution containing a modified soap which. consists of ordinary soap mixed with one or more chlorinated hydrocarbons which are liquid under the conditions of use and also mixed if desired with one or more hydrocarbons which are liquid under those conditions, to remove the ink from such paper. By chlorill nated hydrocarbon I means a chlorine-containing compound which would be a hydrocarbon if all of its chlorine atoms were replaced by hydroen atoms.

Much study has been given to the removal of carbon inks from paper, and various processes and compounds have been proposed for that purpose. Some good results have been obtained; but none are known that are fully satisfactory.

For instance, aqueous soap solutions in conjunction with certain liquid hydrocarbons, particularly naphtha (gasoline) and kerosene, have been used with good efiect, sometimes with and sometimes without some'added alkali, such for instanceas sodium carbonate.' (See the Kinyon and Kinyon Patent No. 1,826,179, granted October 6,-1931.) The liquid hydrocarbon is an organic solvent which is believed to play a dual role. w

1. It dissolves a binder which prior to such 85 dissolving caused the carbon-black particles to adhere to one another and to the paper.

2. It is apparently adsorbed on the surface of the carbon-black particles, and thereby forms a coating which is repellant to a greater or less 40 extent tothe moist cellulose of the paper or paper-pulp.

As a result of this, it is thought, there is formed a suspension of carbon black in water, and this suspension is stabilized by the added soap; and the suspension of carbon black can be separated from the cellulose fibers by collecting such fibers upon a screen and washing with water, leaving the washed fibers, which are relatively white and freefrom carbon (ink), on the screen. Q

In practice, however, the [combination of soap solutions with hydrocarbons such as gasoline and kerosene has in many cases notbeen satisfactqry. Certain binders which are used in ink, and

especially in printers ink, are not adequately dissolved in such liquid hydrocarbons, which at best are rather feeble solvents of many organic compounds. In consequence, with many inks, the carbon-black particles which are held toether by the binder of the original ink, espe- 5' cially certain printers inks, are imperfectly dispersed in the soap solution, and in consequence the paper pulp which is obtained shows undesir-, able black specks, which render it salable only with difliculty and at a lowered price.

I have discovered that great improvement can be obtained in the cleansing'of paper pulps, with a much cleaner resultant paper pulp, if chlorinated hydrocarbons instead of, or'in addition to, simple hydrocarbons are combined with 15 the ordinary soap. A great number of such chlorinated hydrocarbons may be used, for they are effective as a class, and more efiectivd than are the corresponding simplehydrocarbons; although, of course, some are more efiective than 2 others. It is essential only that the chlorinated hydrocarbon be in liquid phase at the temperahire at which the cleansing operation is carried on; and that temperature may vary from ordinary room temperature to a temperature just be- 25 low the boiling point of water, as requiredby the character of the cleansing to be done.

Examples of chlorinated hydrocarbons which may efiectively be combined with soap to produce a more effective cleansing agent for use 30 in my process for removing ink from, printed Paper are:

1. The monochlorides and/or polychlorides (dichlorides, trichlorides, tetrachlorides, etc.) of the paraflin hydrocarbons, such as methane, 35 ethane, propane, butane, isobutane, pentane, isopentane.

2. The monochlorides and/or polychlorides of benzene.

3. Ethylene polychlorides, such as ethylene and tetrachloroethylene.

The chlorinated hydrocarbons which I prefer are:

a. Ethylene dichloride.

b. Trichloroethylene.

c. 1,3-dichloroisobutane (also called 1,3-dichloro-2-methylpropane.)

d. Amylene dichlorides, described below.

The various chlorinated hydrocarbons, not only' the four which are listed as preferable but also 50 the others listed generically, may be used either separately or in groups, to combine with soap to produce the desired cleansing agent for removing ink from printed paper. Some of the chlorinated hydrocarbons, however, cannot be trichlorod0 used alone, on account of having too low a boiling point or too high a melting point, for the boiling point should be higher and the melting point should be lower than the temperature of the deinking operation; but such chlorinated hydrocarbons can often then be used in conjunction with other chlorinated hydrocarbons. Thus, for instance, methyl chloride is not suitable alone because of its low boiling point, and hexachlorobenzene is not suitable alone because of its high melting point; but either of these may be used when mixed with other chlorinated-or simple hydrocarbons of suitable melting and boiling points.

Further, it is not necessary that these chlorinated hydrocarbons be in pure form. Excellent results are obtainable by various mixed commercial chlorinated hydrocarbons.

As one example of this, excellent results are obtained by the so-called amylene dichlorides, which is a mixture of polychlorides of pentane and isopentane consisting principally of dichlorides and produced as a byproduct in the commercial production of monochloropentanes from the chlorination of mixed pentanes (n-pentane and isopentane). These amylene dichlorides have heretofore had little use, but they are found to be very effective in conjunction with soap and water in removing printers ink from paper.

As another example of available mixed chlorinated hydrocarbons is the mixture of polychlorides which is obtained by the chlorination of isobutane as described in the application of Earl T. McBee and myself, Serial No. 590,046, filed February 1, 1932. These polychlorides of isobutane include the 1,3-dichloride, a mixture of the 1,1- dichloride and the 1,2-dichloride with the latter in preponderating amount, the 1,2,3-trichloride, and the 1,1,2,3-tetrachloride. Any of these various isobutane polychlorides alone, or a mixture of any two or more or all of them, is very eflective as an aid to soap and water in the de-inking of paper.

The chlorine in these chlorinated hydrocarbons is in no sense a bleaching agent, as is sodium hypochlorite which has previously been suggested to bleach inks. I remove ink instead of bleaching it. The color in. printers ink is due to carbon black, which is a soot containing a large percentage of free carbon and which cannot be bleached without injuring or destroying paper. The chlorinated hydrocarbons which I use function as solvents and adsorbates, and not as chemical bleaching agents.

The following is an example of my invention, given for illustration and not for limitation.

One pound of any ordinary commercial soap is dissolved in 160 gallons of soft water. To'this solution is added about 1 ounce of chlorinated hydrocarbon, such as amylene dichlorides' or trichloroethylene, or ethylene dichloride, or, one or more of the aforesaid polychlorides of isobu tane, desirably 1,3-dichloroisobutane. Such a solution is very effective to de-ink old newspapers and magazines.

For such use, I add the old newspapers or magazines to the mixture of soap solution and chicrinated hydrocarbon, with the amount of paper sufficiently small so that the mass is still fluid. Then the mixture with paper is beaten, for an hour or thereabouts, with the whole maintained at a temperature between and 180 F., usually until the paper is comminuted by the combined action of the beating and the solution. The temperature used depends upon the nature of the paper, and on the character and extent of the inking. For example, dense paper with large amounts of filler, and with heavy inking, requires a higher temperature than does ordinary newsprint. After the beating is continued for the desired time, the whole is poured on to a screen, through which the solution is drained off while the pulp is held upon the screen. Often the paper will be found to be sufiiciently whitened in one washing; but if not, the operation may be repeated with a new soap solution modified by the presence of one or more chlorinated hydrocarbons. The solution from later washes may be used on other batches of paper stock for earlier washings thereof, until the solution becomes too dirty for further use. The paper pulp after being obtained in sufliciently whitened state by washing and beating with my modified soap solution is then desirably rinsed with soft water.

A variation of the modified soap which I may use for this de-inking involves the'addition to the de-inking solution of some unchlorinated hydrocarbon, or mixture of unchlorinated hydrocarbons, which is liquid at the temperature used for the de-inking operation. This is in addition to the soap and the chlorinated hydrocarbon or hydrocarbons, for it is essential to my invention that chlorinated hydrocarbons be included. When I add unchlorinated hydrocarbons, what I prefer is ordinary naphtha or gasoline.

An example of a suitable de-inking solution which contains both chlorinated and unchlorinated hydrocarbons is' as follows:

One pound of any ordinary commercial soap is dissolved in gallons of soft water. To this solution is added between one-half ounce and one ounce of one or more of the chlorinated hydrocarbons already referred to, such as amylene dichlorides or ethylene dichloride or a trichloroethylene or 1,3-dichloroisobutane. In addition there is added about one-half ounce to one ounce of unchlorinated hydrocarbon or hydrocarbons, such as naphtha. Preferably the amount of unchlorinated hydrocarbon is sochosen that the specific gravity of the mixed chlorinated and unchlorinated hydrocarbons is slightly less thanunchlorinated hydrocarbon or hydrocarbons, I

may add such chlorinated hydrocarbon or hydrocarbons, and if desired an unchlorinated hydrocarbon or hydrocarbons, to the soap while the latter is still in the crutcher. In this way I can obtain directly in solid form a modified soap which contains the reagents which I have found desirable for use in de-inking paper. In this case, the' quantity of chlorinated hydrocarbon or hydrocarbons, and of the unchlorinatedhydrocarbon or hydrocarbons if they are used, is desirably about 3% to 6% by weight of the soap proper. When the chlorinated hydrocarbon or hydrocarbons, and if desired the unchlorinated hydrocarbon or hydrocarbons, are thus made a part of the soap proper it is desirable to use those which have relatively high boiling points, so' that evaporation losses during storage and transit will not be too great.

when this modified soap is being used, it is suitably dissolved in water, and forms a soap solution in which the chlorinated hydrocarbon or hybon or hydrocarbons if such be present, are emulsified. This solution or mixture may be used in the manner already outlined.

- The examples given above are for illustration only. Many variations may be made. The concentration of the soap solution, the ratio of chlorinated hydrocarbon to soap, the ratio of unchlorinated hydrocarbon (if used) to chlorinated hydrocarbon and to soap, the ratio of paper to solution, the temperature and time of beating operation, and the number of beating operations, may all be varied to conform to the characteristics of the particular paper stock and the amount and character of ink on it, and in accordance with the demands of economics in the process.

In the examples which I have given above I have not included in the modified soap any free alkalies or alkaline salts, and for many purposes I prefer that there shall be no free alkalies or alkaline salts. However, when and if desired, I may add in any of these examples a small amount of a suitable alkali or alkaline salt such for instance as sodium metasilicate, other sodium silicates, trisodium phosphate, sodium tetraborate, sodium hydroxide, or other alkalies or alkaline salts, which as already stated have been used in other detergent operations in which cellulosic material soiled with carbonaceous matter is cleansed. For instance, with the proportions of either of the examples given, I might add from one-quarter to one-half ounce of sodium hydroxide.

I claim as my invention:

1. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and one or more chlorinated hydrocarbons.

- 2. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and one or more chlorinated hydrocarbons and one or more unchlorinated hydrocarbons.

3. The process of de-inking paper which bears a carbon ink, which consists in acting upon such vated temperature.

5. The process of de-inking paper which bears a carbon ink, which consists in beating such paper in an aqueous solution containing soap and one or more chlorinated hydrocarbons.

6. The process of de-inking paper which bears a carbon ink, which consists in beating such paper in an aqueous solution containing soap and one or more chlorinated hydrocarbons and one or more unchlorinated hydrocarbons.

7. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and ethylenedichloride. I

8. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and trichloroethylene.

9. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and one or more polychlorides of isobutane.

10. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and 1,3-dichloroisobutane.

11. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and amylene dichlorides.

12. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and one or more chlorinated hydrocarbons at a temperature between and F.

13. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with anaqueous solution containing soap and one or more chlorinated hydrocarbons. and subsequently washing the paper pulp in soft water.,

14. The process of de-inking paper which bears a carbon ink, which consists in acting upon such paper with an aqueous solution containing soap and one or more chlorinated hydrocarbons an an alkali or alkaline salt.

. ,HENRY B. HASS. 

